Solve for $r$ : $-28 + r = 28$
Explanation: Add $28$ to both sides: $ \begin{eqnarray} \\ -28 + r &=& 28 \\ \\ {+28} && {+28} \end{eqnarray} $ $ \begin{eqnarray} \hphantom{-28 + r} &\hphantom{=}& \hphantom{28} \\ r &=& 28 {+ 28} \\ \end{eqnarray} $ Simplify. $ r = 56$